BACKGROUND: Metastatic deposits to the breast from extramammary neoplasms are rare. Clinically and radiologically, metastatic neoplasms may mimic primary benign and malignant neoplasms of the breast. A correct diagnosis of metastasis to the breast is of considerable importance since the treatment of primary and secondary malignancies of the breast is different. CASES: Six cases of metastatic neoplasms in the breast were diagnosed by fine needle aspiration biopsy (FNAB). The cases included poorly differentiated squamous carcinoma of the cervix, endometrial adenocarcinoma, gastric signet-ring cell carcinoma, small cell carcinoma of the lung, large cell carcinoma of the lung and plasma cell myeloma. Four of the patients were female and two male. Four had a previously diagnosed extramammary malignancy, but in two cases the breast mass was the first manifestation of cancer. A correct cytologic diagnosis was made in all six cases. CONCLUSION: FNAB can distinguish metastatic deposits from primary breast tumors even when this is the first presentation of an extramammary neoplasm. A good knowledge of cytomorphology and histomorphology, together with clinical correlation and comparison with previous cytologic/histologic material, will prevent an incorrect diagnosis.